cannot export to EPS at correct size?

Hello all
I have had a problem for a long time now and do not seem to be able to find
a solution. I need to export drawings from AutoCAD v14 to Illustrator for
artwork design. When Illustrator opens my DWG or DXF files, they are
massively scaled up and I cannot find a solution to this. However, I can
export to EPS BUT this gives me further problems. If I chose the option 'fit
to page' the drawings are very small and all need to be scaled up after
opneing in Illustrator. If I uncheck this option, my drawings appear correct
to scale BUT I do not et all of the drawing. I have only noticed today, that
after exporting to EPS, AutoCAD notes on its command line that the effective
plotting area is something like '190.5 x 266.5' and this happens to be the
size of the image that opens in Illustrator. How can I alter this effective
plotting area? I have no option to do this in the EPS options window? I can
change the paper size, but not the plotting area. I have of course tried
changing the options of 'What to plot...' from the display to window etc.
but I knwe already that this was not the answer as all my drawing was on the
screen anyway. It seems to be to do with this effective plotting area I
think, but how to change this?
Thanks all
Chris